1. Field of the Invention
The present invention relates to the field of oil filters, and more particularly to oil filters as are frequently used on internal combustion engines.
2. Prior Art
Internal combustion engines, including gasoline and diesel engines as are commonly used in cars, trucks, boats and stationary power plants, frequently use a canister type oil filter for filtering the crankcase oil as it circulates through the pressure lubrication system. A typical filter of this type may be seen in FIG. 1. Such filters are characterized by a can-like housing 20 with a top cap 22 permanently attached thereto having an internally threaded center region or hub 24, openings 26 and a flat rubber seal 28. Within the can-like housing 20 and separating the center region in communication with the opening through hub 24 and the outer region in communication with the openings 26 is a pleated paper filter material through which oil may pass. In use, the threaded center hub 24 threads onto a short threaded pipe on the oil filter mount on the engine until rubber member 28 seals against a flat surface on the oil filter mount. Porting adjacent the short threaded pipe-like protrusion on the oil filter mount provides oil communication with the openings 26. Normally oil flow is through the openings 26, through the paper filter and then out through the threaded pipe-like structure threaded into hub 24.
Filters of the type shown in FIG. 1 have the primary advantage of being easily replaced by simply unscrewing the used filter and screwing a replacement filter back on. However, they also have certain disadvantages, since not only is the filter element (the paper filter) effectively replaced on each oil change, but the pressure container in which the filter element is mounted is also replaced on each oil change. Consequently, the cost of these filters substantially increases the cost of the oil change itself. Further, because of the wide variety of filter sizes, a substantial number of filters must be inventoried to have an adequate supply of the various sizes that may be required. Also, the filtering of the paper is less than ideal, the paper catching only a percentage of particles of a given size, with the paper clogging over time so that increasing percentages of the recirculating oil bypasses the filter entirely.
While filters of the foregoing type are easily removed from an engine and replaced with a new filter, the used filter is not easily disposed of. Being toxic, the used filter cannot simply be thrown out, so to speak, as before, but rather must be disposed of using prescribed and relatively expensive procedures. Consequently, there is room for improvement in both the performance and the economics of internal combustion engine oil filters.